Reimplement CheckClass and IsPointerEqual functions

- The definition of FxGlobalFunctionCall_CheckClass was big and scary. I
  would say this is a big improvement, since now it gets to leverage the
  same framework that action functions use.
- The definition of FxGlobalFunctionCall_IsPointerEqual was not so big and
  scary, so this can't be called so much of an improvement as
  CheckClass was. (Which is not to say that it isn't better anyway.)

src/thingdef/thingdef_codeptr.cpp

@@ -152,6 +152,67 @@ bool ACustomInventory::CallStateChain (AActor *actor, FState *state)
 	return !!result;
 }
 
+//==========================================================================
+//
+// CheckClass
+//
+// NON-ACTION function to check a pointer's class.
+//
+//==========================================================================
+
+DEFINE_ACTION_FUNCTION(AActor, CheckClass)
+{
+	if (numret > 0)
+	{
+		assert(ret != NULL);
+		PARAM_PROLOGUE;
+		PARAM_OBJECT	(self, AActor);
+		PARAM_CLASS		(checktype, AActor);
+		PARAM_INT_OPT	(pick_pointer)		{ pick_pointer = AAPTR_DEFAULT; }
+		PARAM_BOOL_OPT	(match_superclass)	{ match_superclass = false; }
+
+		self = COPY_AAPTR(self, pick_pointer);
+		if (self == NULL)
+		{
+			ret->SetInt(false);
+		}
+		else if (match_superclass)
+		{
+			ret->SetInt(self->IsKindOf(checktype));
+		}
+		else
+		{
+			ret->SetInt(self->GetClass() == checktype);
+		}
+		return 1;
+	}
+	return 0;
+}
+
+//==========================================================================
+//
+// IsPointerEqual
+//
+// NON-ACTION function to check if two pointers are equal.
+//
+//==========================================================================
+
+DEFINE_ACTION_FUNCTION_PARAMS(AActor, IsPointerEqual)
+{
+	if (numret > 0)
+	{
+		assert(ret != NULL);
+		PARAM_PROLOGUE;
+		PARAM_OBJECT	(self, AActor);
+		PARAM_INT		(ptr_select1);
+		PARAM_INT		(ptr_select2);
+
+		ret->SetInt(COPY_AAPTR(self, ptr_select1) == COPY_AAPTR(self, ptr_select2));
+		return 1;
+	}
+	return 0;
+}
+
 //==========================================================================
 //
 // A_RearrangePointers

wadsrc/static/actors/actor.txt

@@ -66,6 +66,9 @@ ACTOR Actor native //: Thinker
 	native fixed_t meleerange;
 	native fixed_t speed;
 
+	native bool CheckClass(class<Actor> checkclass, int ptr_select = AAPTR_DEFAULT, bool match_superclass = false);
+	native bool IsPointerEqual(int ptr_select1, int ptr_select2);
+
 	// Meh, MBF redundant functions. Only for DeHackEd support.
 	action native A_Turn(float angle = 0);
 	action native A_LineEffect(int boomspecial = 0, int tag = 0);